Effects of grain shape and size on milling yields in wheat. II. Experimental studies

Abstract

The relationships between grain size and shape and milling yield were examined in samples of 11 current commercial cultivars and breeding lines of wheat grown at several sites in northern New South Wales. In addition, the effects of segregation within samples for grain size and test weight were studied. For samples that had been segregated for test weight, there was a strong positive correlation between test weight and milling yield. This correlation was much weaker for samples of different varieties grown at a particular site although over all sites the correlation was significant. Similarly, in samples stratified for grain size, there was a consistent positive correlation between seed size and milling yield as expected on theoretical grounds. In contrast, in samples of different cultivars grown at the one site, grain size was not correlated with milling yield. These contrasting results were taken to indicate that the contribution of differences in seed size to genotypic difference in milling yield were small relative to the effects of other factors. The effects of some of these other attributes of wheat grains, which may influence milling yield (e.g. the amount of germ tissue, thickness of bran, depth of crease), were also studied. Free-milling wheats appeared to differ from their poorer milling counterparts in several of these factors, each of which appeared to make a minor but cumulative contribution to differences in milling yield. No one factor studied here appeared on its own to make a major contribution to genotypic difference in milling yield.